The invention relates to a device for the discharge of flowable granular material from flexible and more particularly sack or bag-like containers by means of a discharge aspiration device adapted to be introduced into the container from above along with a lifting assembly or tackle which engages the top part of the container using vertically movable holding elements adapted for expanding or drawing out the container.
In many fields of industry and more especially in the plastics manufacturing industry, the starting materials are in the form of flowable granular material. Such materials are frequently delivered in the form of filled canisters, so-called octabins, which are lined with an interior foil, that is to say, they have an interiorly placed foil sack, which surrounds the granular or bulk material. Furthermore, for the storage and transport of granular materials, folding boxes having an interiorly arranged foil sack, fabric sacks and/or fiber-reinforced sacks are employed. Also, bags known as big-bags may be employed, in which case, no exterior reinforcing container is provided.
Discharge from such containers is principally performed using aspiration devices, an aspiration tube like a lance, which is driven into the granular material. A disadvantage in this respect is however that such aspiration tube must be continuously swept, i.e., caused to perform a follow-up motion by hand rather like the aspiration tube of a vacuum cleaner in order to ensure an optimum depth of immersion into the material at the desired position of aspiration. This means that an operator is occupied at the point of aspiration constantly, or at least for extended periods of time. Moreover, it is not possible to avoid the foil frequently being drawn against the aspiration tube so that the aspiration operation is interrupted.
If, however, such manual sweeping action of the aspiration tube is not performed, the effect is that although the aspiration tube sucks in a part of the granular material, in the case of bins for granular material with a diameter of a meter or more, remote fractions of the granular material will not move to the point of aspiration. As the level of the material in the bin goes down, the problem becomes increasingly serious because it is hardly possible for a slope to form from the edge of the bin to the deepest position of aspiration.
It is furthermore a known practice to place foil-lined, filled bins on a tilting device and by tipping the tilting device to cause the material to be delivered at a particular point. Such a tilting device is, however, technically relatively complex and requires a large amount of space. Furthermore, such tipping equipment may not be employed to partly empty fabric sacks.
The German Patent Publication 4,218,331 A1 discloses an emptying device for discharging flowable granular material from flexible containers utilizing a discharge aspiration device. However, in this case, the granular material container is suspended at its top edge using tension springs, which represent vertically moving tilting tackle. The points of suspension at which such tension springs are attached are located just outside the base area of the shipping containers so that the top edge part of the granular material container is drawn outward owing to the tensile force of the springs in a radial direction. In the case of this known suspension device, there is however the danger that on emptying the granular material container by aspiration using a downwardly introduced discharge device, such suction effect will take place principally in the middle of the granular material container and less in the edge parts thereof so that craters will frequently be formed. This will mean that the granular material will be at a higher level in the marginal parts of the granular material container than in the middle. There will then be the danger that at certain times, the aspiration device located in the center of the granular material container will be unable to draw in any granular material, since the middle part has been cleared of material, and on the other hand, collapse of the marginal parts of the granular material will mean that the tip of the aspiration device will be relatively deeply buried. Orderly aspiration is impeded by this effect. A particular disadvantage is furthermore that owing to cratering, full discharge of the granular material from the container is only possible with difficulty or to an insufficient extent.